Fast enough to circumnavigate the earth 3 times an hour, once every 20 minutes. It is 1/4 mile long with width and depth greater than a football field. Its speed alone would set the earth’s atmosphere on fire. A true MOAB.
We’d never know what hit us.
For those on the other side of the world from impact, there’d be no radio or TV. MAYBE a little internet.
But their time would be limited. Within a day or two the toxic gases would reach them too.
Planet extinction event.